1. Field of the Invention
The present invention relates to a scratch card printer for preparing a scratch card with printed information, such as a character or image, covered for concealment in which the concealed character or image can be visualized by scratching the covered material off the card surface by a nail, a coin, etc.
2. Description of the Related Art
Conventionally, the main printing method of a scratch card for use in the private lottery, etc., is by a printing machine. In this printing system, a form plate corresponding to a character, an image, etc., is initially prepared so as to initially print it on cards. With the use of such a form plate, card printing is effected in large quantities. In a printing machine where an ink for concealment is set, printing is made on cards in a manner to cover the printed character, an image, etc., with a concealing material. In this way, scratch cards have been produced in large quantities. In this case, separate printing methods are used one for effecting printing based on the form plate by which a character, an image, etc., are printed on cards and one for effecting printing with such character, image, etc., covered with a concealing material. This separating method is suited to mass production of scratch cards one at a time.
Another printing method is also considered by which printing is effected with a generally known thermal printer to obtain scratch cards. In this printing system, for example, a character, an image, etc., are printed on a card by heating an ink ribbon or underlying heat-sensitive sheet by means of a thermal head. After the thermal head has been set to a condition under which printing is made by the thermal head with the thermal ribbon for concealment, printing is done so as to conceal the character, an image, etc., with a cover material. In this connection it is to be noted that, after such concealing printing, the operator has to reset the thermal head back to an original position.
The thermal transfer ribbon for covering the printed character, the image, etc., on the card for concealment has been known, some having a matte layer and heat-melting ink layer on a film base material and some having a heat-resisting layer on the other surface of such a film base material so as to prevent any adverse effect from a sticking due to a heat from the thermal head as well as from a wrinkle upon making of printing (for example, JPN PAT APPLN KOKAI PUBLICATION No. 2001-113889).
For such separate printing methods in which one printing is made on a card based on a form plate corresponding to a character and image and another printing is made in a manner to cover such a character and image, etc., with a concealing material, it is appropriate to make printing on cards in large quantities. In this separate method, it is necessary to prepare many plate forms corresponding to many kinds of characters and images. Further, there is the case where only a small number of cards are required for respective kinds of them and, even if many scratch cards are prepared, more are left in stock, so that these methods are not appropriate. Since, in the latter printing method, the operator has to change the settings of printing a plurality of times, these operations become very cumbersome. Where two printers are used one to print the character, image, etc., on the cards and one to make concealing printing in a manner to cover the character, image, etc., for concealment, more installation space is required and added costs are involved.
Though the character, image, etc., are printed on the cards, no correct printing control corresponding to the characteristic of the thermal transfer ribbon for concealment is done upon the making of concealing printing to cover the character, image, etc. That is, when solid printing is done while heating the thermal transfer ribbon for concealment, printing control is done with an equal energy upon the making of solid printing on a printing area of the card. Since, however, a metal material is contained in an ink layer of the thermal transfer ribbon, a viscosity curve becomes gentler with respect to the temperature. If printing is done under the above-mentioned printing control, no sharp edge is obtained at the final end edge portion of an printing area and there occur bleeding, blurring, reverse transfer, etc., so that a printing quality thus obtained becomes deteriorated.